@media screen and (min-width: 0px) and (max-width: 499px) {
    .c ,.c1,.c2,.c3 {
        width: 99%;
        float: none;
    }

@    media screen and (min-width: 500px) and (max-width: 959px) {
        .c {            width: 780px;
        margin: 0 auto;
    }

    .c1,.c2,.c3 {
        margin: 10px 0;
        float: left;
    }

    .c1 {
        width: 240px;
    }

    .c2 {
        width: 500px;
    }

    .c3 {
        width: 760px;
    }
}

@media screen and (min-width: 960px) {
    .c {
        width: 960px;
        margin: 0 auto;
    }

    .c1,.c2,.c3 {
        margin: 10px 0;
        float: left;
    }

    .c1 {
        width: 300px;
    }

    .c2 {
        width: 620px;
    }

    .c3 {
        width: 940px;
    }
}

